Definition Sexually transmitted disease, or STD, refers to any contagious disease that is transmitted from one person to another during sexual contact.

What is going on in the body? Diseases are passed from one person to another in many ways. The common cold, for example, could be caught during sexual activity. However, the cold is not considered a sexually transmitted disease because sex is not the main way a cold is transferred from one person to another.

Sexual activity refers to contact between the genitals of one partner and the genitals, anus, eyes, mouth, or throat of the partner. An STD may be transmitted by bacteria, a virus, or a parasite. These micro-organisms can enter the body and infect the skin and mucous linings of the vagina, rectum, urethra, cervix, eyes, mouth, and throat. STDs can be spread by heterosexual or homosexual relations.

What are the signs and symptoms of the disease? Sexually transmitted diseases can cause a wide variety of symptoms. Commonly, STDs may cause the following symptoms:

pain, which is most commonly in the urethra. The urethra is the tube that carries urine from the bladder to the outside of the body. The pain may get worse during urination. Pain can also be in the anus, throat, or eyes, depending on the type of sexual contact.

skin rash or other lesions, which can have many different appearances, and may be painful or painless

Other symptoms will depend on the type and severity of the sexually transmitted disease. Some people may have no symptoms but will be able to transmit the disease to others.

What are the causes and risks of the disease?The organisms that cause sexually transmitted diseases are passed from one partner to another during sexual intercourse. Any other intimate contact of the genitals, mouth, rectal area, or the sharing of sexual toys can also transmit the organism from one individual to another.

The most common STDs are as follows:

gonorrhoea, caused by the Neisseria gonorrhoeae bacterium. This condition primarily causes pain and a fluid discharge in the affected area.

chlamydia, caused by the Chlamydia trachomatis bacterium. This STD may also cause pain and a fluid discharge in the affected area.

syphilis, caused by the Treponema pallidum bacterium. Untreated syphilis causes a painless skin rash and many other effects, including heart and brain damage.

Other STDs are less common. Having multiple sex partners and not using condoms increases the risk of STDs. Having sex with those more likely to have STDs, such as prostitutes, also increases the risk. Open lesions or sores on the skin or inside the mouth increase the likelihood of catching an STD when skin-to-skin exposure takes place during sexual activity. Oral or anal sexual practices can expose a person to a greater load of organisms.

What can be done to prevent the disease? While the only way to prevent STDs is to avoid sex, safer sex practices help lower the risk. Having sex with only one person who is faithful and known to be disease-free can also prevent STDs from occurring. The use of male condoms or female condoms reduces, but does not eliminate, the risk of catching an STD. Other forms of birth control, such as oral contraceptives or a diaphragm, do not provide protection from STDs. Epidemics of STDs exist in most parts of the world.

How is the disease diagnosed? Diagnosis of sexually transmitted disease begins with a history and physical examination. Further tests will be performed depending on the STD suspected.

A culture may be done to diagnose some STDs, including chlamydia and gonorrhoea. Culture is a method used to grow organisms in the laboratory, which helps doctors identify the particular infection. A specimen of tissue, such as a sample of liquid discharge, is put in a special material to help the organism grow. The organism can then be identified a few days later under a microscope. Newer tests can diagnose certain STDs, such as Chlamydia, within minutes. Previously, test results were not available for a day or two.

With STDs such as trichomonas or Syphilis, the organism can be seen in a sample of discharge with a microscope.

HIV, hepatitis B, and certain other STDs require a blood test to make the diagnosis.

Pubic lice can be seen as tiny bugs in the pubic hair, usually with a microscope or magnifying glass.

What are the risks to others? All sexually transmitted diseases are contagious. Those who have an STD should not have sexual contact with another person until they receive treatment or until the infection has cleared. All STDs can be transmitted to babies while they are in the uterus or during delivery. Effects of STD infection on babies depend on the disease transmitted and effectiveness of treatment. Effects can include localised infections, congenital abnormalities, or even death.

What are the treatments for the disease?Chlamydia, gonorrhoea, trichomonas, pubic lice, and syphilis can be cured with antibiotics. Genital herpes, hepatitis B, and HIV cannot be cured, but they often can be treated with medications to lessen symptoms and damage to the body. Genital warts from human papilloma virus can be removed, but the warts may come back. All sexual partners need to be informed, tested, and treated, if necessary.

What are the side effects of the treatments? Antibiotics may cause allergic reactions, stomach upset, and rash. The methods used to destroy genital warts may irritate or damage nearby healthy skin.

What happens after treatment for the disease? Many sexually transmitted diseases can be cured completely. It is important to notify and treat all sexual partners to prevent spreading of the STD. If a partner is not treated, the affected person may catch the STD again. Some long-term effects of STDs, such as infertility from chlamydia or gonorrhoea, are not reversed by treatment. Other STDs, such as HIV or hepatitis B, may get worse over time with or without treatment.

How is the disease monitored? Some STDs need no monitoring after treatment. Others, such as HIV and hepatitis B, need frequent blood tests to monitor the effects of the disease on the body. Any new or worsening symptoms should be reported to the doctor.

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